It is proposed to study the effects of dysregulated CF production (GM-CSF, G-CSF, Multi-CSF) alone and in combination with expression of the oncogenes myc, raf/myc and bcr/abl on murine myeloid leukemia development. The objective is to develop murine models for human myeloid leukemia development by reproducing the suspected autocrine production of CSF in some human leukemias, the known translocations involving oncogenes, particularly bcr/abl and the CSF dependence for proliferation. For this purpose a mouse line having a CM-CSF transgene and recombinant retroviruses containing the CSF genes and oncogenes will be used. Multipotential stem cells and committed progenitor cells will be infected with MPZen(GM-CSF), MPZen(Multi-CSF) or MPZen(G-CSF) and transplanted into lethally-irradiated recipients or cultured in semisolid medium. The in vivo studies will attempt to determine whether autocrine and/or elevated levels of CSF production alter multipotential cell (CFU-S) proliferation and/or commitment. These parameters will be analyzed by studying individual spleen colonies for cellular morphology and CFU-S content, ability of infected multipotential cells to compete in competitive repopulation assays and by viral integration patterns. The in vitro studies will be performed to determine whether autocrine production compared to exogenous addition of purified CSF's alters committed progenitor cell proliferation and/or differentiation. In all cases, animals and in vitro cultures will be monitored to determine whether dysregulated CSF production predisposes cells to leukemic transformation. Complementation studies will also be performed by infecting transgenic GM-CSf bone marrow cells with retroviral vectors containing myc, raf/myc or bcr/abl. In addition, normal bone marrow cells will be infected with the CSF or oncogene retroviruses in various combinations and sequences. These studies aim to determine whether autocrine CSF production in combination with oncogene expression increase myeloid leukemic transformation.